Piston Actuated Split Input Transmission Synchronizer

ABSTRACT

A piston actuated synchronizer system for a split torque transmission where the piston is attached directly to the synchronizer shift collar on the synchronizer centerline to provide the required actuation in a small volume of space and resolve fork and rod deflection issues seen on other synchronizers that use such a system. The piston is pressure applied and spring released. This design also uses a displacement sensor to monitor synchronizer engagement.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a divisional and claims the priority benefitof copending U.S. patent application Ser. No. 12/347,972, filed Dec. 31,2008, which disclosure is incorporated herein by reference.

TECHNICAL FIELD

This patent disclosure relates generally to multiple range transmissionsand, more particularly to a split input continuously variabletransmission that provide multiple ratio ranges and uses one or moresynchronizers when shifting between ranges.

BACKGROUND

Because of the limited speed range of most prime mover devices, e.g.,engines, motors, etc., such devices are frequently used in conjunctionwith a transmission to provide a range of transmission input-to-outputratios, e.g., 3-to-1, 1-to-1, or 1.5-to-1 (overdrive). Certain ratiosprovide lower torque at higher speed, while other ratios provide highertorque for lower speed, i.e., during acceleration or hill climbing. Suchdiscrete ratio transmissions, while useful and ubiquitous, causediscontinuities during operation that may be disconcerting or otherwisedisruptive. As such, continuously variable transmissions (CVTs) havebeen developed to allow smooth acceleration without sharpdiscontinuities between ranges, and such transmissions are now inwidespread use. However, while CVT transmissions do not require shiftsbetween discrete ratios, they do generally require shifts between ratioranges. For example, a first ratio range may allow transmission ratiosfrom 3-to-1 up to 2-to-1, while a second range may allow transmissionratios from 2-to-1 and 1-to-1. In order to provide ratios from 3-to-1 upto 1-to-1, therefore, a range shift will be needed.

While existing systems use fork activated shifting with some success,this type of activation is not optimal for every configuration, due tospace constraints. Moreover, fork activated shifting systems imposemaintenance and replacement requirements due to the action of spinningtransmission components against the shift forks. However, the shiftforks also serve to gauge the position of the transmission componentsand the completion of each shift. Thus, the industry has experienceddifficulty in attempting to design a split path CVT shifting system thatprovides the benefits of fork-activated shifting within a limited volumeand without the attendant wear problems caused by the forks.

SUMMARY

In an aspect of the disclosed principles, a split path CVT is providedfor selectively providing multiple transmission ratio ranges between aCVT input and a CVT output. In this aspect, one or more of the ratioranges are shifted by a piston-actuated synchronizer system. Thepiston-actuated synchronizer system includes a cylindrical collarconnected by a spline to a piston sharing a common rotational axis. Thecollar is also part of the synchronizer assembly. A cylindrical drivengear has a spline associated with it on a second common rotational axisthat is coincident with the first common rotational axis. The gearspline is connected to the synchronizer output ring. The gear issupported on the shaft by a bearing and can rotate independently fromthe shaft. The cylindrical collar, axially movable along the secondcommon rotational axis, engages the synchronizer hub to the synchronizeroutput ring to engage the shaft to the gear.

A piston is associated with the cylindrical collar. The piston issupported by the hub, which is connected to the shaft, the hub alsohaving one or more fluid inlets formed therein in fluid communicationwith the cylindrical cavity. The hub is partially enclosed by amanifold. The fluid inlets in the hub coincide with fluid passages inthe manifold. The fluid passages in the manifold coincide with fluidpassages in the housing. The flow of fluid from the one or more fluidinlets into the cylindrical cavity is regulated by a solenoid valve onthe housing to force the piston and the associated cylindrical collaraxially toward the synchronizer to engage the synchronizer hub to thesynchronizer output ring and therefore to the gear. In an embodiment, aspring is provided for biasing the collar away from the synchronizerengaged position.

Further aspects and features of the disclosed principles will beappreciated from the following detailed description and the accompanyingdrawings, of which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic system diagram showing a split path CVTenvironment within which the disclosed principles may be implemented;

FIG. 2 is a partial cross-sectional side view of a piston-actuatedsynchronizer system within a split path CVT according to one aspect thedisclosed principles, wherein the piston-actuated synchronizer is notengaged;

FIG. 3 is a partial cross-sectional side view of a piston-actuatedsynchronizer system within a split path CVT according to one aspect thedisclosed principles, wherein the piston-actuated synchronizer isengaged; and

FIG. 4 is a flow chart illustrating a process of range shifting withinan embodiment of the disclosed principles.

DETAILED DESCRIPTION

This disclosure relates to machines requiring a transmission to link apower source to the final ground-engaging mechanism, e.g., wheels,tracks, etc., and/or to another powered function or implement. Examplesof such machines include machines used for mining, construction,farming, transportation, or any other industry known in the art. Forexample, the machine may be an earth-moving machine, such as a wheelloader, excavator, dump truck, backhoe, motor grader, material handleror the like. Moreover, one or more implements may be connected to themachine for a variety of tasks, including, for example, loading,compacting, lifting, brushing, and include, for example, buckets,compactors, forked lifting devices, brushes, grapples, cutters, shears,blades, breakers/hammers, augers, and others.

FIG. 1 is a diagrammatic illustration showing a transmissionarchitecture 100 within which embodiments of the disclosed principlesmay be used. The illustrated transmission architecture 100 includes anengine 101, a variator 103, and a split path CVT 105. In addition, acontroller 107 is included in order to coordinate the operation of theengine 101, variator 103, and split path CVT 105. A first output shaft109 provides a first input from the engine 101 to the split path CVT105, and a second output 111 provides a second input from the variator103 to the split path CVT 105. A third output 113 from the split pathCVT 105 is provided for linkage to a final drive train or other powertransfer system, not shown. The third output 113 provides a weightedcombination of the inputs to the split path CVT 105. More precisely, ata given engine speed, the effective transmission ratio of the split pathCVT 105 will depend upon the speed and direction of the variator 103 aswell as upon a range setting of the split path CVT 105.

The engine 101 is an example of a primary mover, but it will beappreciated that other primary mover systems may be used additionally oralternatively without departing from the scope of the describedprinciples. Similarly, the variator 103 is simply an example of asecondary mover, and it will be appreciated that other types ofsecondary movers may be used additionally or alternatively withoutdeparting from the scope of the disclosed principles of operation.

The operation of the engine 101 is controlled based on one or moreinputs, including, for example, an input from a user interface (notshown), e.g., a pedal or lever, as well as an input from the controller107, e.g., for purposes of torque control, fraction control, etc. Theoperation of the variator 103 is controlled by the controller 107 basedon the current and desired state of the split path CVT 105. Finally, thesplit path CVT 105 is managed by the controller 107 based on a number ofparameters including, for example, available engine power and torque, aswell as vehicle speed.

The controller 107 may be any computing device capable of sensing one ormore conditions of the split path CVT 105, engine 101 and/or variator103 and providing control outputs to one or more of the split path CVT105, engine 101 and/or variator 103. By way of example but notlimitation, the controller 107 may be integrated with an engine ormachine control module, or may be a separate device. The controller 105operates by reading computer-readable instructions from acomputer-readable medium and executing the read instructions. Thecomputer-readable medium may be a tangible medium such as a hard drive,optical disc, jump drive, thumb drive, flash memory, ROM, PROM, RAM,etc., or may be an intangible medium such as an electrical or opticalwave form traveling in air, vacuum, or wire.

Although shift forks have traditionally served to execute accurate shifttiming in split path CVT architectures, the use of these forks is notwithout consequence. The forks are non-rotating members that mustforcefully interface with rapidly rotating transmission parts to executea shift. Because rapid shifts are required, high shift loads may beapplied, causing substantial wear to the forks and/or the matingtransmission surfaces. Such wear necessitates maintenance and repair,both of which can be costly. Typically, the forks and the otherassociated parts of the system also require a fair amount of spatialvolume to accommodate their bulk and range of motion.

In an embodiment of the disclosed principles, a piston-actuated shiftmechanism is introduced to execute one or more range shifts in the splitpath CVT 105. Although various configurations may be used withoutdeparting from the scope of the disclosed principles, one exemplaryconfiguration is shown in cross-sectional side view in FIG. 2 and FIG.4. The illustrated piston-actuated shift mechanism 200 includes acylindrical driven gear 201 and a cylindrical collar 205 that mayselectively couple or uncouple the gear 201 to the shaft 225 via thesynchronizer 203. The collar 205 surrounds and is keyed to asubstantially annular piston 213. The piston 213 is axially slidable ona hub 209, to selectively engage or disengage the driven gear 201 via aspline 207.

A cylindrical compression spring 206 is located between the piston 213and the synchronizer 203 to bias the assembly including the force collar205 away from the spline 207. A distal end of the collar 205 furthestfrom the spline 207 is formed into or joined with the cylindrical piston213, which fits closely on the hub 209, forming a cylindrical cavity 215there between. The hub 209 is attached to the shaft 225 by bolt 221. Thecylindrical cavity 215 is filled and drained of pressurized hydraulicfluid via one or more fluid inlets 219. The hydraulic fluid is suppliedthrough passages in the manifold 239 and in the housing 217.

A solenoid valve 237 on the housing 217 is controlled via the controller107 to regulate the flow of fluid from the one or more fluid inlets 219into the cavity 215 The solenoid valve 237 may be proportional or binary(switching) and is electronically controlled by a solenoid controlsignal in an embodiment. However, other types of solenoid control may beused instead, including mechanical or hydraulic control for example. Itwill be appreciated that as pressurized fluid is introduced into thecavity 215 via the one or more fluid inlets 219, the piston 213 isforced forward, compressing the return spring 206 as in FIG. 3.

The collar 205 has an annular step 242 thereon to engage a flange 241 ofthe piston 213. Thus, the action of displacing the piston 213 alsoaxially displaces the collar 205 towards the spline 207. If sufficientfluid is introduced into the cavity 215, the displacement of the collar205 will be such that the collar 205 causes the synchronizer 203 toreduce the relative speed difference of the shaft 225 and the gear 201to zero. This allows the collar 205 to move axially to engage the spline207 of the synchronizer output ring which is engaged to the gear 201through spline 227.

In an embodiment of the disclosed principles, the engagement of thecollar 205 with the spline 207 is used as a threshold precondition tofurther accelerate the shaft 225. This is because any acceleration priorto the engagement of the driven collar 205 with the spline 207 willdelay synchronization and will cause excessive wear to the synchronizerfriction material.

To this end, a displacement sensor 229 is adapted to detect the axialposition of the collar 205 and to convey a signal indicative of theaxial position of the collar 205 to the transmission controller 107 viaa sensor output 231. The displacement sensor 229 may be of any suitabletype and configuration, but in an embodiment of the disclosedprinciples, the displacement sensor 229 comprises a magnetic sensor. Inan alternative embodiment, the displacement sensor 229 comprises atwo-state switch. The displacement sensor 229 detects the axial locationof the sensor target 233 that is contained in the sensor target keyway235 in the piston 213. The sensor target 233 is prevented from rotatingby the displacement sensor 229.

FIG. 4 is a flow chart illustrating a process of range shifting withinan embodiment of the disclosed principles. The illustrated process 400begins at stage 401, wherein the controller 107 receives or generates anacceleration command to accelerate the split path CVT output. TheController 107 causes the split path CVT output to accelerate via thevariator 103 and/or engine 101 at stage 403. The Controller continues toaccelerate the split path CVT output at stage 405. In stage 407, thecontroller 107 determines whether a shift point has been attained. Ifsuch a point has been reached, the Controller 107 first reduces thetorque output by the engine 101 and variator 103 at stage 409, and thenactivates the solenoid valve 237 at stage 409 to fill the chamber 215with pressurized hydraulic fluid, driving the piston 235 forward.

At stage 413, the controller determines whether the driven collar 205has engaged the spline 207. This can be determined based on a reading ofthe signal from the displacement sensor 229. Once it is determined thathe driven collar 205 has engaged the spline 207, the controller 107increases the torque applied by the engine 101 and variator 103 at stage415 to resume the prior rate of acceleration.

INDUSTRIAL APPLICABILITY

The described principles are applicable to machines requiring atransmission to link a power source to the final ground-engagingmechanism, e.g., wheels, tracks, etc., and/or to another poweredfunction or implement. Examples of such machines include machines usedfor mining, construction, farming, transportation, or any other industryknown in the art. For example, the machine may be an earth-movingmachine, such as a wheel loader, excavator, dump truck, backhoe, motorgrader, material handler or the like. Exemplary implements include,without limitation, buckets, compactors, forked lifting devices,brushes, grapples, cutters, shears, blades, breakers/hammers, augers,and others.

In this context, the disclosed principles allow rapid shifts in a splitpath CVT without the replacement and maintenance requirements imposed bythe exclusive use of fork shifters. It will be appreciated, however,that a split path CVT generally involves multiple sets of gears thatmesh and unmesh to shift the range of the transmission. Moreover, it iscontemplated that certain range shifts can still be executed via forkshifters, such that the CVT includes a combination of one or morepiston-actuated shift mechanisms as described herein and one or moretraditional fork shift mechanisms.

It will be appreciated that the foregoing description provides examplesof the disclosed system and technique. However, it is contemplated thatother implementations of the disclosure may differ in detail from theforegoing examples. All references to the disclosure or examples thereofare intended to reference the particular example being discussed at thatpoint and are not intended to imply any limitation as to the scope ofthe disclosure more generally. All language of distinction anddisparagement with respect to certain features is intended to indicate alack of preference for those features, but not to exclude such from thescope of the disclosure entirely unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context.

1-10. (canceled)
 11. A process of range shifting in a split path CVThaving a first input driven by an engine and a second input driven byanother power source, the CVT also having an output and supportingmultiple ratio ranges between the first input and the output, as well asa piston-driven synchronizer actuated via a solenoid valve, the methodcomprising: receiving an acceleration command to accelerate the splitpath CVT output; causing the split path CVT output to accelerate;determining that a shift point has been attained; in response todetermining that a shift point has been attained, reducing a torque atone or both of the first and second inputs; activating the solenoidvalve and thereby actuating the piston of the synchronizer; determiningthat the range has been shifted; increasing the torque applied at one orboth of the first and second inputs to resume the prior rate ofacceleration.
 12. The process of range shifting in a split path CVTaccording to claim 11, wherein causing the split path CVT output toaccelerate further comprising causing one of the variator and the engineto accelerate.
 13. The process of range shifting in a split path CVTaccording to claim 11, wherein reducing a torque at one or both of thefirst and second inputs further comprises reducing a torque at one orboth of the engine and variator.
 14. The process of range shifting in asplit path CVT according to claim 11, wherein determining that the rangehas been shifted comprises detecting a position of a range shiftingmember via a position switch.
 15. The process of range shifting in asplit path CVT according to claim 11, wherein increasing the torqueapplied at one or both of the first and second inputs to resume theprior rate of acceleration comprises increasing the torque applied atleast one of the engine and the variator.
 16. A controller for executinga process of range shifting in a split path CVT having a first inputdriven by an engine and a second input driven by another power source,the CVT also having an output and supporting multiple ratio rangesbetween the first input and the output, as well as a piston-drivensynchronizer actuated via a solenoid valve, the controller having acomputer-readable medium containing computer-readable instructionsincluding: instructions for receiving an acceleration command toaccelerate the split path CVT output; instructions for causing the splitpath CVT output to accelerate; instructions for determining that a shiftpoint has been attained; instructions for reducing a torque at one orboth of the first and second inputs in response to determining that ashift point has been attained; instructions for activating the solenoidvalve and thereby actuating the piston of the synchronizer; instructionsfor determining that the range has been shifted; instructions forincreasing the torque applied at one or both of the first and secondinputs to resume the prior rate of acceleration.
 17. The controlleraccording to claim 16, wherein the instructions for causing the splitpath CVT output to accelerate further comprise instructions for causingone of the variator and the engine to accelerate.
 18. The controlleraccording to claim 16, wherein the instructions for reducing a torque atone or both of the first and second inputs further comprise instructionsfor reducing a torque at one or both of the engine and variator.
 19. Thecontroller according to claim 16, wherein the instructions fordetermining that the range has been shifted comprise instructions fordetecting a position of a range shifting member via a position switch.20. The controller according to claim 16, wherein the instructions forincreasing the torque applied at one or both of the first and secondinputs to resume the prior rate of acceleration comprise instructionsfor increasing the torque applied at least one of the engine and thevariator.